Selectable lethality, focused fragment munition and method of use

ABSTRACT

A munition and method capable of producing real-time selectable effects ranging from unrestricted to low collateral damage. The munition is capable of a directionally focused fragment pattern and limited lethality/damage effects.

This invention was made with Government support under FA8651-07-C-0153 awarded by the United States Air Force and Government support under W911QX-10-C-0019 awarded by the United States Army. The Government has certain rights in the invention.

FIELD OF THE INVENTION

The current invention relates to the field of munitions capable of directionally focused fragmentation.

BACKGROUND OF THE INVENTION

Munitions are typically designed for the specific purpose of creating the maximum lethality or destruction for a given munition volume or weight. Typical munitions utilize a metal case containing explosive material. Detonation of the explosive material fragments the case into high velocity shrapnel that damages or obliterates the target(s). These types of munitions are highly indiscriminant in that they will produce substantial damage within a large lethality radius. Such design has been beneficial in conventional force-on-force warfare where collateral damage is of minimal concern.

Current warfare is frequently conducted by small groups of combatants in areas that may be highly populated with non-combatants, or with remotely fired missiles targeting a specific target located in or near a populous area. In such situations, traditional munitions can produce undesirable collateral damage to personnel and property. In recent years, effort has been placed on creating selectable effects munitions for attacking a target with little or no resultant collateral damage.

Guirguis (U.S. Pat. No. 7,347,906 B1) describes an on-demand variable yield munition that permits the selection of low, high, or intermediate collateral damage. Such munitions could decrease collateral damage in war zones, but the Guirguis munition's blast footprint is limited to a radial area surrounding the munition; it offers no forward-focused lethality option. Guirguis also fails to describe or claim the desirable feature of post-launch lethality selection. Thus Guirguis does not satisfy the need for real-time selectable effects munitions that offer the post-deployment choice of generalized outputs that can range from blast only to blast plus fragments to a prescribed fragment footprint including a forward-focused lethality area.

The inventors herein describe and claim a device and method that satisfies the need for on-demand, selectable effects, multi-mode munitions that can be adapted in real time to address and respond to evolving circumstances on the battlefield. The present invention was described in a 2010 symposium paper, incorporated herein by reference. Dennis Wilson, John Granier, Christopher Vineski, and Donald Littrell, “Development of a Small Selectable Mode Warhead,” 12th Joint Classified Bombs/Warheads & Ballistics Symposium, Monterey, Calif., 23-26 Aug. 2010. The present invention is an apparatus and method that accommodates the constantly changing circumstances of current warfare and provides options from which the user can in real time select the type, magnitude, and direction of the explosive force that a munition will deliver to a target. The present invention gives the user the ability to select the characteristics of a munition as it is in transit to the target.

The preferred embodiment of the present invention apparatus is a real-time selectable effects, multi-mode munition that is appropriate for both unrestricted and low collateral damage scenarios. The selectability provides several benefits over state of the art munitions. One benefit is enhanced mission flexibility. For example, aircraft-delivered, real-time selectable effects, multi-mode munitions eliminate time-consuming and costly returns to the air base for proper weapon load-out in the event of post-takeoff changes in target intelligence. Another benefit is streamlined logistics. Real-time selectable effects, multi-mode munitions can decrease the number of unique munitions required to engage diverse target scenarios. Most importantly, real-time selectable effects, multi-mode munitions provide discriminating lethality against a broad target set, thus minimizing collateral personnel damage and costly post-conflict infrastructure reconstruction.

Guirguis uses two conventional organic explosives that have well defined detonation velocities that effectively establish the respective power outputs. The conventional explosives have fixed energies of detonation and heats of combustion that combine to set the total effective energy output. The selectable effects achieved by the present invention are based on its use of a modified high-energy density explosive that releases its energy via variable speed self-oxidized combustion (SOC). The SOC reaction rate is determined by the shock impetus strength. Because the rate and extent of an SOC reaction depend on the initiation stimulus, the reaction is shock dependent and can be overdriven. Aluminized perfluoropolyether modified explosives are attractive for selectable effects applications because the combustion wave speed, and thus the energy release rate or power, can be controlled through novel initiation techniques. The modified explosive enables the present invention's novel option of selectable fragmentation, i.e., isotropic or anisotropic fragment projection as opposed to the strictly spherical fragmentation of state of the art munitions.

SUMMARY OF THE INVENTION

The following terms in this application and any continuation applications based thereon shall be construed using the corresponding inventor-supplied definitions.

“Case” shall mean an enclosure of any geometry such as, but not limited to, a casing.

“Explosive” shall mean a material capable of releasing energy at detonation time scales.

“Modified explosive” shall mean any material capable of fast energy release by means of a multi-molecular diffusion reaction as opposed to the typical single molecule reaction such as a C-H-N-O explosive.

“Fragment” shall mean a piece detached from a whole, including, but not limited to, fractured metal casing, pieces of a pre-formed geometric array, and metal particulates.

“Reactive metal and oxidizer” shall mean materials that when combined and provided the appropriate initiation energy produce a combustion reaction.

“Selectable effects” shall mean output or results that can be chosen by a user.

“Variable yield” shall mean the result achieved by tuning the total energy or power output from a munition.

In the apparatus preferred embodiment, the real-time selectable effects multi-mode munition contains an outer case enclosing at least two types of explosives. One end of the case has a fragmentable end cap while the other end has at least two detonators designed to selectively detonate the two different explosives.

In another embodiment, the munition case contains at least two explosives. Each end of the munition contains a detonator designed to selectively detonate one of the explosives.

In another embodiment, at least one of the explosives is a reactive metal and oxidizer combination.

In yet another embodiment, the method of selectively detonating the real-time selectable effects multi-mode munition is based on user input.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section view of a cylindrical assembly illustrating one embodiment of the current invention.

FIG. 2 shows an end view of a focused fragment array end cap.

FIG. 3 shows a section view of a cylindrical assembly illustrating a second embodiment of the current invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the preferred embodiment of the current invention apparatus has a case 100 that has a preformed focused fragment end cap 200 on one end and a detonator housing 140 on the other end. The detonator housing 140 is secured to the case 100 with the threaded retaining ring 120, but could also be integral with the case. The detonator housing 140 contains the first detonator 510. The case 100 also contains a shock attenuating detonator housing 160 and a second detonator 520. The shock attenuating detonator housing 160 significantly reduces the transmitted shock pressure. It is comprised of a homogeneous, low density, highly compressible material, but can also be comprised of a heterogeneous, highly dissipative material such as soft granular particles. Shock attenuating detonator housing porosities can range from 10% to 50%. Examples include, but are not limited to, polymers such as polyethylene and polystyrene, and epoxy containing hollow micro-spheres.

The case 100 also contains explosives 300 and 400 such that explosive 300 is directly initiated by detonator 510, and explosive 400 is initiated by detonator 520. Booster explosive 515 facilitates initiation of explosive 300. Explosive 300 forms an outer cylinder in contact with the case 100 and surrounds the inner core of explosive 400. Explosive 400 is generally cylindrical in form and is in contact with the focused fragment end cap 200 that is attached to the case 100. The end cap can be retained by an adhesive or a mechanical feature such as, but not limited to, machine threads.

Pressure generated by detonation of explosive 300 causes the case 100 to fragment into many small fragments moving outward with high velocity. One skilled in the art can recognize that this can be accomplished by fabricating case 100 from various metals including, but not limited to, low and high carbon alloy steel, powder metals, and cast metals. The case 100 may be designed to break up into predetermined fragment sizes.

However, the pressure generated by the reaction of explosive 400 is not sufficient by itself to shatter the case 100 into small, high-velocity fragments. The case 100 is designed to contain the pressure so that the focused fragment end cap 200 ruptures into high velocity fragments projected away from the munition in a direction substantially co-linear with the munition's longitudinal axis. FIG. 2 shows the end view of the focused fragment end cap 200. In the preferred embodiment, the focused fragment end cap 200 is constructed from multiple hexagonal tungsten segments 820 held together by a low-strength encapsulating matrix to form a circular disk or other suitable shape. The low-strength encapsulating matrix can be, but is not limited to, thermoset epoxies, thermoplastics, sintered metals, and polymer/metal powder mixtures. The fragmenting end cap can be an array of other nesting shapes and sizes such as, but not limited to, millimeter size spheres, cubes, or cones. While tungsten is the preferred material, other materials such as, but not limited to, steel and tantalum can be used. Alternatively, the focused fragment end cap 200 may be constructed from a single piece of metal or ceramic scored to break apart into segments of predetermined shape and size.

In yet another embodiment, the focused fragment end cap 200 is made from a combination of tungsten powder and polymeric matrix or other suitable binder. A density in the range of 8 to 16 g/cc is used in the preferred embodiment, although one skilled in the art will recognize that other densities can be used. In this embodiment the end cap ruptures and many fine particles are blasted away from the munition in a direction substantially co-linear with the munition's longitudinal axis. While tungsten is the preferred material, other materials including, but not limited to, tantalum or mixtures of high-density metals can be used.

In the preferred embodiment, the first explosive 300 is an explosive such as, but not limited to, C-4, H6, RDX, or HMX. The second explosive 400 is a modified explosive such as, but not limited to, a mixture of combustible metals and oxidizers with or without a low concentration of HMX or RDX. A critical requirement of the modified explosive 400 is that it not cause a detonation of explosive 300.

In operation the invention is initiated in various modes. In one mode of operation, the first detonator 510 is activated, thus initiating the first explosive 300. This in turn initiates the second explosive 400. This mode results in both explosives being detonated, and the case 100 and focused fragment end cap 200 breaking into many small fragments projecting in many different directions with a result similar to that of traditional munitions.

In a second mode of operation, the second detonator 520 is activated, thus initiating the second explosive 400. The reaction is not sufficient to cause the first explosive 300 to detonate; however, it does cause the explosive 300 to deflagrate. The case 100 is designed to contain the resultant pressure so that the focused fragment end cap 200 ruptures into high velocity fragments moving away from the munition in a direction substantially co-linear with the munition's longitudinal axis.

In a third mode of operation, both detonators 520 and 510 are activated either simultaneously or with a delay specified by the user. This mode produces blast and fragmentation characteristics unique from the two modes previously described. One skilled in the art will appreciate that there are numerous means of creating a time delay between the two initiators, including, but not limited to, electronic, mechanical, and pyrotechnic means.

An embodiment of the current invention was fabricated utilizing a case 100 made from AISI 4140 steel with an inside diameter of 1.5 in., length of 3.5 in., and a wall thickness of 0.300 in. In another embodiment low carbon alloy 1018 steel was used. The first explosive 300 was approximately 100 g of PETN sheet explosive, and the second explosive 400 was approximately 200 g of aluminum and perfluoropolyether. The focused fragment end cap 200 utilized 48 hexagonal tungsten pellets epoxied together. The first detonator 510 was a standard RP-502 product, and the second detonator 520 was a standard RP-87 product with a 1 g PBXN-5 booster pellet. While the current invention utilized the above-mentioned dimensions, one skilled in the art could scale the invention up or down. One skilled in the art will also recognize that the detonators and explosives can be selected from a large population for customizable results.

In an alternative embodiment depicted in FIG. 3, the case 100 contains explosive 300 and explosive 400. Both ends of the housing have a focused fragment end cap (210 and 220). The focused fragment end cap 210 contains a first detonator 520, and the focused fragment end cap 220 contains a second detonator 510. The explosive 300 can be directly initiated by the detonator 510, and the explosive 400 can be directly initiated by the detonator 520. Booster explosive 525 facilitates initiation of explosive 400. End caps 210 and 220 are metal/polymeric matrices intended to shatter when impinged by low pressure input. End caps 210 and 220 can also be made of monolithic materials such as, but not limited to, steel and tungsten.

Explosive 300 lines the inside of the case 100 and is in contact with the detonator 510.

Explosive 400 is partially contained within the explosive 300 and is in contact with the detonator 520. A portion of explosive 400 is in contact with the inside of the case 100 near the focused fragment end cap 210. This configuration allows explosive 400 to be initiated resulting in a fast SOC reaction and deflagration of explosive 300.

An unrestricted collateral damage output can be achieved by activating detonator 510, detonating explosive 300. Similarly, both detonators 510 and 520 can be activated simultaneously. Either method will fracture the case 100, producing small, high velocity fragments and a reaction of explosive 400.

For limited or low collateral damage, detonator 520 is activated alone. This initiation mode results in a controlled SOC reaction of explosive 400 and simultaneous deflagration of explosive 300. The resulting high pressure ruptures the end caps 210 and 220 producing a dense metal cloud. The resulting multi-phase blast creates a small lethality radius. End caps 210 and 220 can be designed to produce fragments ranging from micron to millimeter size. The metal cloud fragments can be, but are not limited to, tungsten and tantalum. The case 100 either remains intact or separates into several large, low velocity fragments having a limited lethality radius.

Initiation of detonators 510 and 520 in various timed sequences produces a variety of blast and fragmentation characteristics intermediate to the output modes previously described.

The present invention includes a method for using the present invention apparatus for achieving a desired blast result. The munition as described herein is delivered to a desired target via aircraft, ships, wheeled or track vehicles, dismounted troops, or a combination of those and other means. During delivery, target environment data are analyzed for determination of the desired output mode. If maximum damage with unrestricted collateral damage is required, the detonator 510 or both detonators 510 and 520 is/are armed upon launch and activated when the munition is near the target. If, during the mission, intelligence dictates a change from unrestricted to limited collateral damage, only the detonator 520 is armed and activated. If an alternative result is desired, a real-time command specifies the time delay between the two detonations. The detonator real-time selection, arming, timing, and activation can be achieved with commonly understood wireless or wired signal technology. 

1. A variable lethality, focused fragment munition comprising: a) a case at least partially containing a first and a second explosive; b) at least one end cap partially containing said explosives; and c) at least a first and a second detonator.
 2. The munition of claim 1 wherein said second explosive forms a core inside said case and said first explosive at least partially fills any space between said case and said second explosive.
 3. The munition of claim 1 further comprising at least one shock attenuating detonator housing at least partially containing at least one said detonator.
 4. The munition of claim 1 wherein said end cap is a focused fragment end cap in communication with said second explosive.
 5. The munition of claim 4 wherein said focused fragment end cap is comprised of a frangible material.
 6. The munition of claim 4 wherein said focused fragment end cap is comprised of aggregated fragments.
 7. The munition of claim 4 wherein said focused fragment end cap is comprised of aggregated metal fragments.
 8. The munition of claim 7 wherein said metal fragments are selected from the group consisting of steel, tungsten, and tantalum.
 9. The munition of claim 6 wherein said aggregated fragments have major dimensions ranging from 100 microns to 1 centimeter.
 10. The munition of claim 1 wherein said first detonator is in communication with said first explosive, and said second detonator is in communication with said second explosive.
 11. The munition of claim 1 wherein said first explosive is selected from the group consisting of C-4, H6, RDX, CL-20, and HMX.
 12. The munition of claim 1 wherein said second explosive is comprised of a metal and an oxidizer.
 13. The munition of claim 12 wherein said metal is selected from the group consisting of aluminum, boron, magnesium, silicon, tantalum, zirconium, zinc, titanium, calcium, and lithium.
 14. The munition of claim 12 wherein said oxidizer is selected from the group consisting of perfluoropolyether, perfluoropolyether diol, polytetrafluoroethylene, tetrafluoroethylene, fluorinated ethylene propylene copolymer, and chlorotrifluoroethylene.
 15. The munition of claim 12 further comprising RDX.
 16. The munition of claim 12 further comprising HMX.
 17. The munition of claim 1 further comprising more than two explosives.
 18. A method of using a variable lethality, focused fragment munition comprising a case at least partially containing a first and a second explosive, at least one end cap partially containing said explosives, and at least a first and a second detonator, said method comprising: a) delivering said munition to a target; b) acquiring data about said target during said delivery of said munition; c) analyzing said data; d) at least partially based on said analysis of said data, determining a desired mode of operation for said munition; and e) sending at least one signal to said munition wherein at least one said signal configures said munition for a desired lethality prior to arrival of said munition at said target.
 19. The method of claim 18 wherein at least one said signal configures said munition for ignition of a desired number of said detonators onboard said munition.
 20. The method of claim 18 wherein at least one said signal configures said munition for a desired timing sequence of ignition of a desired number of said detonators onboard said munition. 